Differentials are known in the automotive industry as devices that split engine torque two ways, allowing each output to spin at a different rate. Generally, differentials have three primary tasks: to aim the engine power at the wheels; to act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before being transferred to the wheels; and to transmit the power to the wheels while allowing them to rotate at different speeds.
In a typical vehicle application, the rotating driveshaft of the vehicle engages a ring gear, which is mounted onto the differential housing. Thus, the driveshaft drives the ring gear, which in turn rotates the differential housing. A typical mechanical differential contains a housing (or carrier), two side gears, and several pinion gears. Pinion shafts attach the pinion gears to the housing so that as the housing rotates the pinion gears are driven. Specifically, inputting torque to the housing drives the pinion shaft that, in turn, drives the pinion gears. The pinion gears drive the two side gears, which in turn drive the axle (or half shafts) attached thereto.
Locking differentials are used predominantly on vehicles intended for off the road use, such as tractors, agricultural machines, military vehicles, all terrain vehicles, etc. Frequently, the half-shafts of off-road vehicles will experience different resistive couples due to, for example, the roughness of the ground and/or a slippery surface. In such a case, if the differential is not partially or totally excluded from functioning, then the half-shaft or the wheel experiencing the least amount of resistance from the ground will receive the majority of the power. As a result, the vehicle will lose traction.
Conventional locking differentials are constructed such that the pinion gears are mounted to the differential casing or housing and the differential input gear. The side gears engage the pinion gears to rotate the left and right axles. A typical locking differential includes apertures in the differential housing to allow locking pins to enter therethrough and engage the side gear. Therefore, the differential housing is locked so as not to transmit torque through the gear set by the locking pins engaging the side gears. When the differential is locked, e.g. the locking pins engage the side gear, the rear axles are locked together and rotate at the same speed. When the differential is to be unlocked, the locking pins are removed from the side gear and the rear axles are permitted to rotate at different speeds.
The locking pins are typically mounted to a circular collar. Therefore, when the collar is engaged, the collar and locking pins move axially relative to the differential housing. Specifically, the locking pins slide within the differential housing into engagement with the side gear, thus locking the differential housing relative to the gear set.
FIG. 1 illustrates a known locking differential design having five radial apertures 3 located symmetrically about a side gear 4. FIG. 2 illustrates a known differential housing 5 having locking apertures 6 that are positioned to correspond to the apertures 3 of the side gear 4. Specifically, the locking apertures 6 are spaced symmetrically about the housing 5. FIG. 3 illustrates a known collar 8 having equally symmetrically spaced pins 7 for engagement with the locking apertures 6 of the housing 5 and the apertures 3 of the side gear 4.
FIG. 4 illustrates how the components of FIGS. 1-3 interact in a known differential assembly 9. Specifically, the differential assembly 9 includes the differential housing 5, the side gears 4 and pinion gears 2. The known differential locking assembly 9 also has a bearing journal 11 formed therethrough. The bearing journal 11 is sized to receive front axles or rear axles of a vehicle (not shown) that are connected to the side gears 4.
A pinion shaft 10 attaches the pinion gears 2 to the housing 5. The collar 8 moves about the bearing journal 11 to engage the side gears 4 and the housing 5. The pins 7 are located radially outward from the bearing journal 11. More specifically, the locking pins 7 extend from the collar 8 into the housing 5. In use, each of the pins 7 engage the aperture 3 in the side gear 4 and the locking apertures 6 of the housing 5 to lock the housing 5 to the side gear 4.
Significant machining and complex assembly is needed for such known locking differentials. Particularly, the manufacture of the collar 8 and the locking pins 7 are required to be extremely precise so that each of the locking pins 7 enters each of the locking apertures 6 machined in the differential housing 5. Such manufacturing and assembly has created problems when one of the locking pins 7 is misaligned or one of the locking apertures 6 is slightly off-center. In addition, such precise machining is time-consuming and greatly increases manufacturing costs.
As illustrated in FIG. 4, the locking pins 7 and the locking apertures 6 have been located in a radial pattern significantly larger than the bearing journal 11. In several applications, it is desirable to reduce the overall radial pattern of the locking pins 7 while increasing or at least maintaining the size of the bearing journal 11. Further, there is always a desire to improve the manufacture and assembly of locking differentials.
However, efficient design of the locking differential depends on the size and stresses related to the components. There is a constant need in the art to minimize contact stresses and to achieve a compact sized differential. It is an object of the present invention to address these needs in providing an improved design. Further, there is a constant need in the field to improve upon component design and manufacturing and assembly techniques for locking differentials to reduce costs and time associated with all stages of manufacture and assembly.